1. Field of Invention
The present invention relates to formation sampling to measure resistivity of fluids in formations adjacent well bores.
2. Description of Prior Art
A formation sampling tool known generally as a multiple formation tester has been available from several well logging service companies. Formation testers were primarily used to measure formation fluid pressures at one or two selected depths of interest in a well bore. A feature of the formation tester permitted obtaining as a maximum only two samples of formation fluid during a logging run. The samples were stored in chambers in the formation tester and removed with the tester from the well. The two samples so obtained could then be analyzed at the surface. The gas-oil ratio (GOR) and water cut (WC) measurements of the formation could theoretically then be obtained from the fluid samples. However, the fluid samples obtained normally contained a substantial amount of mud filtrate, which created a major problem in formation water analysis. Partially due to the mud filtrate, the measurements so obtained were treated as only rough predictions of expected petroleum production.